1. Field of the Invention
This invention relates to a carriage moving apparatus for transmitting a driving force to a carriage by a toothed timing belt to thereby reciprocally move the carriage, and a recording apparatus and a reading apparatus using the same, respectively.
2. Related Background Art
In a so-called serial recording apparatus wherein a recording head is carried on a carriage and recording is effected on a recording medium while the carriage is moved, an image is formed on the recording medium while the conveyance of the recording medium and the recording effected with the movement of the carriage are alternately repeated.
The carriage which is main scanning means of the serial type is usually driven by a belt from a drive source such as a motor through pulleys. This belt is usually mounted by two pulleys, and in order to prevent the slack thereof, tension is applied thereto by the pulley on one side.
In order to effect main scanning of higher accuracy, it is generally practiced to prevent bad recording such as slip by the use of a so-called toothed timing belt and toothed timing pulleys which are a belt and pulleys provided with uneven shapes.
There have heretofore been various methods of coupling the timing belt and carriage in such a recording apparatus, and in any of these coupling methods, the belt and carriage are coupled together so that no backlash may be present in that portion of the carriage which is coupled to the belt.
FIG. 8 of the accompanying drawings schematically shows the construction of the belt-coupled portion of a recording apparatus according to the prior art. The belt-coupled portion 101 having a concavity is formed integrally on a carriage 100, as shown, and the concavity has an expause somewhat wider than the thickness of a timing belt 103. One of convex portions defining the concavity is formed with unevenness so as to mesh with the teeth of the timing belt 103, and the timing belt 103 is inserted into the concavity and cylindrical pins 104 are forced thereinto, whereby the timing belt 103 is fixed to the carriage 100.
A method of coupling the concavity of the belt-coupled portion 101 and the timing belt 103 together is such that the timing belt 103 made of an elastic material such as rubber is urged by the fixing pins 104, whereby the carriage 100 and the timing belt 103 are coupled together so that there may be no backlash.
However, such a method of coupling the timing belt 103 and the carriage 100 together in the recording apparatus according to the prior art suffers from the following problems.
In the driving system by the timing belt 103, the timing belt 103 is vibrated by the vibration of a carriage motor which is the drive source of the carriage 100 or the timing belt 103 is vibrated by vibration caused when the toothed timing pulleys and the timing belt 103 mesh with each other. This vibration is sometimes transmitted to a recording head carried on the carriage 100 because the carriage 100 is firmly fixed. This causes bad recording and causes the production of noise such as the resonation of parts incorporated in the carriage 100.
Particularly when a stepping motor is used as the carriage driving motor, the vibration during driving tends to occur.
So, Japanese Patent Application Laid-Open No. 6-47978 proposes a construction as shown in FIG. 9 of the accompanying drawings. That is, a carriage 100 is provided with a coupling hole portion 100a which is formed so as to permit a belt-coupled portion 101 to be loosely fitted therein. Also, unevenness is formed on the belt-coupled portion 101 so as to mesh with the unevenness of a timing belt 103, and a gap for inserting the timing belt 103 thereinto is provided in the belt-coupled portion 101 with the same width as that of the timing belt 103. The timing belt 103 is inserted into this gap, whereafter the belt-coupled portion 101 coupled to the timing belt 103 is further inserted into the coupling hole portion 100a of the carriage 100.
The belt-coupled portion 101 is all or partly formed by a molded article or a member having elasticity. By the belt-coupled portion 101 being thus formed by an elastic member, it is made difficult for the vibration of a carriage driving motor transmitted by the timing belt 103 to be transmitted to the carriage, whereby good image formation is realized.
Also, the belt-coupled portion 101 is loosely fitted in the coupling hole portion 100a provided in the carriage, and this portion also serves to absorb the transmitted vibration.
However, when adopting the construction as described In Japanese Patent Application Laid-Open No. 6-47978, the following problems have been found in obtaining Images of higher dignity,y That is, the belt-coupled portion 101 is loosely fitted to the carriage 100 and therefore, when the carriage 100 is stopped, the backlash of the fitting may affect the stopped position of the carriage. Particularly in this construction, there is a distance between the timing belt engaging portion of the belt-coupled portion and the fitted portion of the belt-coupled portion to the carriage and therefore, an angular moment is applied to the belt-coupled portion 101 and the backlash is increased, and this tends to increase the influence upon the stopped position of the carriage.
If the stopped position of the carriage becomes unstable by such backlash and the choice of the carriage driving construction is mistaken, for example, in an ink jet recording apparatus, the carriage cannot be stopped at a predetermined location due to the presence of the aforementioned backlash when the carriage is to be stopped at the predetermined location in order to bring a cap for protecting the nozzle of a recording head into close contact with the periphery of the nozzle, and leak occurs between the cap and the nozzle and the nozzle dries, and this leads to the possibility that the ink jet recording head becomes incapable of discharging ink.
It is an object of the present invention to provide a carriage moving apparatus which can prevent vibration transmitted from a vibration source such as a motor by a timing belt from transmitting to a carriage, and enhance the stoppage accuracy of the carriage and avoid any inconvenience by the instability of the stopped position of the carriage, and a recording apparatus and a reading apparatus using the same.
It is another object of the present invention to provide a carriage moving apparatus which can reliably effect engagement between a timing belt and a carriage, and a recording apparatus and a reading apparatus using the same.
It is still another object of the present invention to provide a carriage moving apparatus for transmitting a driving force to a carriage by a toothed timing belt to thereby reciprocally move the carriage, which is designed such that belt projected portions provided on the timing belt and having their central axes passing through substantially the widthwise center of the timing belt, and protruding to the opposite sides with the timing belt interposed therebetween are engaged with a carriage engaging portion formed on the carriage.